Automotive burglar alarm that recycles after its initial alarm production

Abstract

An alarm system for an automotive vehicle including direct coupled input connections which provide a voltage proportional to the amount of current interchanged between, the battery and the electrical system of the vehicle. An arming circuit is responsive to the voltage and arms the burglar alarm only when less than a predetermined current is interchanged between the battery and the electrical system. An alarm circuit produces an alarm when the alarm system is armed and more than a predetermined amount of current is drawn from the battery.

We claim: 
     
       1. A burglar alarm for an automotive vehicle having an electrical system including a battery, battery cables, at least one electrical device for drawing current from the battery, and a switch for controlling current flow from the battery to said device, said burglar alarm comprising: input means for sensing an amount of current drawn from and charged to said battery and producing a signal indicative thereof;   arming means, responsive to said signal, for automatically arming said burglar alarm only when said current changes to less than a predetermined amount;   alarm means for producing an alarm indication when said burglar alarm is armed and more than a predetermined current is drawn from said battery, and for maintaining said alarm indication; and   means for resetting said burglar alarm a predetermined time after said indication, and for causing said alarm indication to recur if more than said predetermined current continues to be drawn from said battery.   
     
     
       2. A burglar alarm as in claim 1, wherein said alarm indication recurs only if said arming means has not reset due to said charge to said battery being less than said predetermined amount. 
     
     
       3. A burglar alarm as in claim 1 wherein said alarm means includes a timer, and said means for resetting said alarm indication is a pulse generator, coupled tos aid timer, which produces a pulse during an operation of said timer, said pulse resetting said alarm means. 
     
     
       4. An alarm as in claim 3 wherein said alarm means includes a flip flop, and said pulse generator provides a pulse, which while active provides a reset to said flip flop, and which when completed, ends said reset to allow said alarm to recur, said alarm means producing said alarm indication by latching into an active state only when said reset is removed and said more than a predetermined current is drawn from said battery. 
     
     
       5. A burglar alarm as in claim 3 further comprising an OR gate, one input of which receives an output from said arming means and another input of which receives an output from said pulse generator, an output of said OR gate being coupled to a reset input of said alarm means. 
     
     
       6. A burglar alarm for an automotive vehicle having an electrical system including a battery, battery cables, at least one electrical device for drawing current from the battery, and a switch for controlling current flow from the battery to said device, said burglar alarm comprising: input means for sensing an amount of current drawn from said battery by said at least one device and producing a signal indicative thereof;   arming means responsive to said signal for automatically arming said burglar alarm only when less than a predetermined current is drawn from said battery;   alarm means for producing an alarm indication for a predetermined time when said alarm is armed and more than a predetermined amount of current is drawn from said battery; and   means for ending said alarm indication after said predetermined time and allowing said alarm indication to recur if said alarm means still receives more than a predetermined current drawn from said battery.   
     
     
       7. An alarm as in claim 6, wherein said alarm recurs if said alarm means subsequently receives more than a predetermined amount of current drawn from said battery. 
     
     
       8. An alarm as in claim 7 wherein said arming means is a timer which produces an output after a predetermined amount of time of discharge from said battery of less than said predetermined current, and said alarm means is a flip flop which receives said signal to signal an end of a reset. 
     
     
       9. A burglar alarm as in claim 8 wherein said alarm means also includes means for resetting said flip flop when said alarm indication is produced. 
     
     
       10. A burglar alarm for an automotive vehicle having an electrical system including a battery, battery cables, at least one electrical device for drawing current from the battery, a switch for controlling current flow from the battery to said device; and a charging means for supplying charging current to the battery, said burglar alarm comprising: input means for sensing an amount of current provided to said battery by said charging means and providing a signal indicative thereof;   arming means for arming said burglar alarm responsive to an arming stimulus;   alarm means for producing an alarm indication for a predetermined time when said alarm is armed and more than a predetermined amount of current is drawn from said battery;   a disarming means responsive to said signal for automatically disarming said alarm, and resetting said arming means thereby ending said alarm indication when more than a predetermined current is charged to said battery; and   means for resetting said burglar alarm a predetermined time after said indication, so that said burglar alarm remains armed after said predetermined time only if said current is less than said predetermined amount, and said alarm indication continues to be produced if more than a predetermined current continues to be drawn from said battery.   
     
     
       11. A burglar alarm as in claim 10 wherein said alarm means is a flip-flop, and said arming means releases a reset signal to said flip-flop to arm said burglar alarm responsive to said arming stimulus, said resetting means produces said reset signal to reset said burglar alarm. 
     
     
       12. A method of operating a burglar alarm for an automotive vehicle, comprising the steps of: sensing an amount of current provided to a battery of the vehicle;   automatically arming said burglar alarm only when said current changes from more than a predetermined amount to less than said predetermined amount;   producing an alarm indication when said burglar alarm is armed and more than a predetermined current is drawn from said battery; resetting said arming means at a time during said alarm indication; and     said alarm indication recurring after a predetermined time if said burglar alarm is armed and more than a predetermined current continues to be drawn from said battery, and producing another alarm indication when said burglar alarm is armed and more than a predetermined current is again drawn from said battery.